/// <summary>
/// Returns whether this instance collides with the argument AxisAlignedRectangle.
/// </summary>
/// <param name="rectangle">The AxisAlignedRectangle to test collision against.</param>
/// <returns>Whether a collision has occurred.</returns>
#endregion
public bool CollideAgainst(AxisAlignedRectangle rectangle)
{
UpdateDependencies(TimeManager.CurrentTime);
rectangle.UpdateDependencies(TimeManager.CurrentTime);
// Get world-positioned segment
Segment a = AsSegment();
// Check if one of the segment's endpoints is inside the rectangle
Vector3 endpoint = new Vector3(
(float)a.Point1.X, (float)a.Point1.Y, 0f);
if (rectangle.IsPointInside(ref endpoint))
{
mLastCollisionPoint = new Point(ref endpoint);
return(true);
}
endpoint = new Vector3(
(float)a.Point2.X, (float)a.Point2.Y, 0f);
if (rectangle.IsPointInside(ref endpoint))
{
mLastCollisionPoint = new Point(ref endpoint);
return(true);
}
// Check if the segment intersects any of the rectangle's edges
// Here, prepare rectangle's corner points
Point tl = new Point(
rectangle.Position.X - rectangle.ScaleX,
rectangle.Position.Y + rectangle.ScaleY);
Point tr = new Point(
rectangle.Position.X + rectangle.ScaleX,
rectangle.Position.Y + rectangle.ScaleY);
Point bl = new Point(
rectangle.Position.X - rectangle.ScaleX,
rectangle.Position.Y - rectangle.ScaleY);
Point br = new Point(
rectangle.Position.X + rectangle.ScaleX,
rectangle.Position.Y - rectangle.ScaleY);
Point tempPoint;
// Test if any of the edges intersect the segment
// (this will short-circuit on the first true test)
if (a.Intersects(new Segment(tl, tr), out tempPoint) ||
a.Intersects(new Segment(tl, bl), out tempPoint) ||
a.Intersects(new Segment(bl, br), out tempPoint) ||
a.Intersects(new Segment(tr, br), out tempPoint))
{
mLastCollisionPoint = tempPoint;
return(true);
}
// No collision
return(false);
}
public bool CollideAgainst(AxisAlignedRectangle rectangle)
{
if (mLastDependencyUpdate != TimeManager.CurrentTime)
{
UpdateDependencies(TimeManager.CurrentTime);
}
if (rectangle.LastDependencyUpdate != TimeManager.CurrentTime)
{
rectangle.UpdateDependencies(TimeManager.CurrentTime);
}
// first perform a quick test to see if the Circle is too far
// away from the rectangle
if ((Position.X + Radius < rectangle.X - rectangle.mScaleX ||
Position.X - Radius > rectangle.X + rectangle.mScaleX ||
Position.Y + Radius < rectangle.Y - rectangle.mScaleY ||
Position.Y - Radius > rectangle.Y + rectangle.mScaleY))
{
return(false);
}
// The simple bounding box test from above will eliminate most
// cases. If we get this far, then it is likely that we have a collision
// and a more in-depth test can be performed.
// quick test to see if the circle is inside of the rectangle
if (rectangle.IsPointInside(Position.X, Position.Y))
{
mLastCollisionTangent.X = -(Position.Y - rectangle.Position.Y);
mLastCollisionTangent.Y = (Position.X - rectangle.Position.X);
return(true);
}
// if we got this far, the bounding box of the circle touches the rectangle
// and the center of the circle is not inside of the rectangle. Perform
// the most expensive checks now.
Point centerPoint = new Point(Position.X, Position.Y);
Segment connectingSegment = new Segment();
int numberOfEndpointsClosestTo = 0;
// top segment
Segment segment = new Segment(
new Point(rectangle.Left, rectangle.Top),
new Point(rectangle.Right, rectangle.Top));
if (segment.DistanceTo(centerPoint, out connectingSegment) < Radius)
{
if (segment.IsClosestPointOnEndpoint(ref centerPoint))
{
mLastCollisionTangent.X = -(connectingSegment.Point2.Y - Y);
mLastCollisionTangent.Y = (connectingSegment.Point2.X - X);
numberOfEndpointsClosestTo++;
}
else
{
mLastCollisionTangent.X = 1;
mLastCollisionTangent.Y = 0;
return(true);
}
}
// bottom segment
segment = new Segment(
new Point(rectangle.Left, rectangle.Bottom),
new Point(rectangle.Right, rectangle.Bottom));
if (segment.DistanceTo(centerPoint, out connectingSegment) < Radius)
{
if (segment.IsClosestPointOnEndpoint(ref centerPoint))
{
mLastCollisionTangent.X = -(connectingSegment.Point2.Y - Position.Y);
mLastCollisionTangent.Y = (connectingSegment.Point2.X - Position.X);
numberOfEndpointsClosestTo++;
}
else
{
mLastCollisionTangent.X = 1;
mLastCollisionTangent.Y = 0;
return(true);
}
}
// left segment
segment = new Segment(
new Point(rectangle.Left, rectangle.Top),
new Point(rectangle.Left, rectangle.Bottom));
if (segment.DistanceTo(centerPoint, out connectingSegment) < Radius)
{
if (segment.IsClosestPointOnEndpoint(ref centerPoint))
{
mLastCollisionTangent.X = -(connectingSegment.Point2.Y - Position.Y);
mLastCollisionTangent.Y = (connectingSegment.Point2.X - Position.X);
numberOfEndpointsClosestTo++;
}
else
{
mLastCollisionTangent.X = 0;
mLastCollisionTangent.Y = 1;
return(true);
}
}
// right segment
segment = new Segment(
new Point(rectangle.Right, rectangle.Top),
new Point(rectangle.Right, rectangle.Bottom));
if (segment.DistanceTo(centerPoint, out connectingSegment) < Radius)
{
if (segment.IsClosestPointOnEndpoint(ref centerPoint))
{
mLastCollisionTangent.X = -(connectingSegment.Point2.Y - Position.Y);
mLastCollisionTangent.Y = (connectingSegment.Point2.X - Position.X);
numberOfEndpointsClosestTo++;
}
else
{
mLastCollisionTangent.X = 0;
mLastCollisionTangent.Y = 1;
return(true);
}
}
if (numberOfEndpointsClosestTo > 0)
{
return(true);
}
else // well, this is rare, but it can happen. Collision failed!
{
return(false);
}
}